Added PWG raster generator

Added class plus tests to generate PWG raster files from in-memory bitmaps.

BUG=318373

Review URL: https://codereview.chromium.org/70193006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235022 0039d316-1c4b-4281-b951-d872f2087c98
[Android] Ignore bookmark callbacks till models are loaded.

BUG=318386

Review URL: https://codereview.chromium.org/70753002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235023 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235023